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A novel and versatile approach to construct 12-phenacyl-11H-benzo[b]xanthene-6,11(12H)-dione derivatives through copper-catalyzed cascade reaction of propargylamines with 2-hydroxynaphthalene-1,4-diones has been developed. The procedure is proposed to go through a sequence of 1,4-conjugate addition, intramolecular nucleophilic addition/dehydration, and hydrolysis of alkyne followed by an enol-ketone tautomerization. The reaction provides a new and highly efficient method for the synthesis of 12-phenacyl-11H-benzo[b]xanthene-6,11(12H)-diones by formation of three new bonds and one heterocycle from readily available starting materials in good to high yields (70-88%) with broad functional group compatibility in a single step.
Subject(s)
Copper , Xanthenes , Catalysis , Hydrolysis , Naphthols , Pargyline/analogs & derivatives , PropylaminesABSTRACT
A versatile and highly regioselective FeCl3-promoted tandem cyclization reaction of in situ generated alkynyl o-quinone methides (o-AQMs) with ß-keto esters has been developed on the basis of the mode involving an intermolecular 1,4-conjugate addition/alkyne-allene isomerization/intramolecular transesterification/isomerization cascade. Using this method, a variety of diversely substituted 4-styryl-2H-chromen-2-ones were prepared with good efficiency and exclusive site-selectivity.
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The evidence and evolution of magnetic polarons (MPs) in HgCr2Se4 have been studied by electron spin resonance (ESR), magnetism and conductivity measurements in a temperature range of 5-300 K. A single paramagnetic resonance line is observed in the high-temperature range while multiple resonance lines appear in the low-temperature range. As temperature decreases, the peak-to-peak linewidth ΔH pp shows a minimum at T min ≈ 210 K, with the activation energy fitted by small polaron hopping model consistent with the bottleneck mechanism, providing an evidence for existence of small MPs above T min. The analysis of the temperature dependence of ΔH pp, double integrated intensity I, and g factor of ESR signals, combined with the temperature dependence of magnetization and conductivity, reveals an evolution process from small MPs at zone I (T > T min) to correlated MPs at zone II (T c < T * ⩽ T ⩽ T min) in the paramagnetic regime. Three critical temperatures, T min (≈210 K), T th (≈175 K), and T * (≈121 K), which determine the evolution characteristics of MPs, are distinguished. The magnetic correlation length ξ of Cr3+-Se2--Cr3+ should account for the evolution of MPs.
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Solid state electrochemical cells with synaptic functions have important applications in building smart-terminal networks. Here, the essential synaptic functions including potentiation and depression of synaptic weight, transition from short- to long-term plasticity, spike-rate-dependent plasticity, and spike-timing-dependent plasticity behavior were successfully realized in an Ag/MoOx/fluorine-doped tin oxide (FTO) cell with continual resistance switching. The synaptic plasticity underlying these functions was controlled by tuning the excitatory post-synaptic current (EPSC) decay, which is determined by the applied voltage pulse number, width, frequency, and intervals between the pre- and post-spikes. The physical mechanism of the artificial synapse operation is attributed to the interfacial electrochemical reaction processes of the MoOx films with the adsorbed water, where protons generated by water decomposition under an electric field diffused into the MoOx films and intercalated into the lattice, leading to the short- and long-term retention of cell resistance, respectively. These results indicate the possibility of achieving advanced artificial synapses with solid state electrochemical cells and will contribute to the development of smart-terminal networking systems.
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An important potential application of solid state electrochemical reactions is in redox-based resistive switching memory devices. Based on the fundamental switching mechanisms, the memory has been classified into two modes, electrochemical metallization memory (ECM) and valence change memory (VCM). In this work, we have investigated a solid state electrochemical cell with a simple Ag/MoO3-x/fluorine-doped tin oxide (FTO) sandwich structure, which shows a normal ECM switching mode after an electroforming process. While in the lower voltage sweep range, the switching behavior changes to VCM-like mode with the opposite switching polarity to the ECM mode. By current-voltage measurements under different ambient atmospheres and X-ray photoemission spectroscopy analysis, electrochemical anodic passivation of the Ag electrode and valence change of molybdenum ions during resistance switching have been demonstrated. The crucial role of moisture adsorption in the switching mode transition has been clarified based on the Pourbaix diagram for the Ag-H2O system for the first time. These results provide a fundamental insight into the resistance switching mechanism model in solid state electrochemical cells.
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Binuclear complexes [{(DMOX)CuCl}2(µ-Cl)2] (1), mononuclear complexes [(DMOX)CuBr2] (2) (DMOX = 4,5-dihydro-2-(4,5-dihydro-4,4-dimethyloxazol-2-yl)-4,4-dimethyloxazole) and the pybox Cu(II) complex [(Dm-Pybox)CuBr2] (3) (Dm-Pybox = 2,6-bis[4',4'-dimethyloxazolin-2'-yl]pyridine) were obtained by reactions of CuX2 (X = Cl, Br) with DMOX and Dm-Pybox ligands, respectively. The molecular structures of 1, 2 and 3 have been determined by single-crystal X-ray diffraction analyses. The complexes 2 and 3 are efficient in catalyzing α-amination of ketones and esters through α-bromo carbonyl intermediate. The procedures are environmentally benign methods using molecular oxygen as an oxidant with water as the only byproduct.
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The magnetocaloric effect (MCE) associated with the spin transitions of alternating longitudinal conical (ALC)-mixed conical (MC) and MC-ferrimagnetic (FIM) states in a Ba0.3Sr1.7Co2Fe12O22 single crystal has been investigated. For magnetic field directions applied along either the [120] or [001] directions, the crystal is found to exhibit the conventional and inverse MCE near the ALC-MC (T(N1) = 235 K) and MC-FIM (T(N2) = 348 K) states, respectively. The dependence of the magnetic entropy on the magnetic field also exhibits such sign change behaviors in the MCE, which is attributed to the magnetic field induced gradual collapse of heliconical magnetic order.
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BACKGROUND: Few studies investigated serum uric acid levels in patients with acute ST-elevation myocardial infarction (STEMI). The study was to assess the clinical value of serum uric acid levels in patients with acute ST-elevation myocardial infarction (STEMI). METHODS: Totally 502 consecutive patients with STEMI were retrospectively studied from January 2005 to December 2010. The level of serum lipid, echocardiographic data and in-hospital major adverse cardiovascular events (MACE) in patients with hyperuricemia (n=119) were compared with those in patients without hyperuricemia (n=383). The relationship between the level of serum uric acid and the degree of diseased coronary artery was analyzed. All data were analyzed with SPSS version 17.0 software for Student's t test, the Chi-square test and Pearson's correlation coefficient analysis. RESULTS: Serum uric acid level was positively correlated with serum triglyceride level. Hyperlipidemia was more common in hyperuricemia patients than in non-hyperuricemia patients (43.7％ vs. 33.7％, P=0.047), and serum triglyceride level was significantly higher in hyperuricemia patients (2.11±1.24 vs. 1.78±1.38, P=0.014). But no significant association was observed between serum uric acid level and one or more diseased vessels (P>0.05). Left ventricular end-diastolic diameter (LVEDd) was larger in hyperuricemia patients than in non-hyperuricemia patients (53.52±6.19 vs. 52.18±4.89, P=0.041). The higher rate of left systolic dysfunction and diastolic dysfunction was discovered in hyperuricemia patients (36.4％ vs. 15.1％, P<0.001; 68.2％ vs. 55.8％, P=0.023). Also, hyperuricemia patients were more likely to have in-hospital MACE (P<0.05). CONCLUSIONS: Serum uric acid level is positively correlated with serum triglyceride level, but not with the severity of coronary artery disease. Hyperuricemia patients with STEMI tend to have a higher rate of left systolic dysfunction and diastolic dysfunction and more likely to have more in-hospital MACE.
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Objective To establish a convenient,accurate and practical method for detection of adefovir dipivoxil resistance-as- sociated mutation in hepatitis B virus:rtA181V/T/S and rtN236T mutations.Methods According to HBV complete sequences in GenBank,two pairs of primers were designed to amplify the region of HBV reverse transcriptase in order to introduce a BglI restriction site upon PCR product of wild type (wt) and a BseDI restriction site upon PCR product of rt236 mutant type.After amplification,the PCR products were digested with BglI and BseDI separately.We used this method to detect wild,rt181 mu- tant,rt236 mutant plasmids and 3 chronic hepatitis B patients' serum with obvious ADV resistance-associated mutations.We also tested the sensitivity of this method by mixing the wild and mutant plasmids in different proportions.Results The method could detect rt181 and rt236 mutations simultaneously.The result of RFLP analysis was in accordance with that of DNA se- quencing and cloning analysis.This method could detect the mutants even when they comprised only 10% of the total virus population.Conclusions The PCR-RFLP method with high sensitivity can detect rt181 and rt236 mutations simultaneously.It can be used for early detection of ADV resistance-associated mutation in hepatitis B virus.
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<p><b>OBJECTIVE</b>To study the resistant rate of hepatitis B virus (HBV) to ADV and the dynamic evolution of HBV in lamivudine (Lam)-resistant chronic hepatitis B (CHB) patients.</p><p><b>METHODS</b>Twenty-three Lam-resistant CHB patients were assigned to a 10mg/d ADV monotherapy for 68-116 weeks. The baseline and different time point blood samples after ADV monotherapy were analyzed for ADV-resistant mutations using direct sequencing of PCR products; the evolution of HBV mutations was examined by clonal analysis of serial samples from one patient infected with ADV-associated resistant HBV strains.</p><p><b>RESULTS</b>The cumulative incidence of genotypic ADV resistance at weeks 48 and 96 was 4.3% and 10.5% respectively respectively. The evolution analysis of HBV mutant strains in an ADV-resistant CHB patient showed that the proportion of YMDD mutants gradually decreased with rtA181S mutants increasing over time after ADV monotherapy, and that rtA181S+N236T mutants became the predominant strains during prolonged ADV monotherapy. The addition of Lam to the ongoing ADV treatment had poorer antiviral response in the patient with rtA181S or rtA181S+N236T mutant infection; one clone with multi-drug resistant mutations was selected during Lam and ADV combination therapy.</p><p><b>CONCLUSION</b>Increased risk of adefovir resistance and selection of multi-drug resistant mutations are associated with long-term ADV monotherapy in patients with Lam-resistant chronic hepatitis B.</p>
